1. Field of the Invention
The present invention relates to a multilayer ceramic capacitor or other electronic device, more particularly relates to a small-sized, large capacity electronic device superior in dielectric constant and other electrical characteristics, superior in temperature characteristic even when the dielectric layers are made thin, and high in reliability.
2. Description of the Related Art
In recent years, electrical products have been made increasingly smaller in size and higher in performance. Along with this, electronic devices are also being asked to be made smaller in size and higher in performance. In the case of an electronic device constituted as a multilayer ceramic capacitor, in particular a high capacity and high reliability are being sought.
However, to obtain a small sized, high capacity multilayer ceramic capacitor, the dielectric ceramic layers and internal electrode layers have to be made thin. Along with this, however, the reliability ends up deteriorating. On the other hand, to obtain a small sized, high reliability multilayer ceramic capacitor, the dielectric ceramic layers and internal electrode layers have to be made thin, but with this a high capacity cannot be obtained.
As a method for obtaining a high capacity and high reliability multilayer ceramic capacitor, for example, Document 1 (Japanese Patent Publication (A) No. 5-9066) proposes a dielectric ceramic composition satisfying the EIA X7R characteristic, exhibiting a high dielectric constant, and having a high insulation resistance. However, with the method shown in this Document 1, for example, when making the dielectric ceramic layers a thin 3 μm or less, it is not always possible to obtain a reliability satisfying the demands of the market.
Further, Document 2 (Japanese Patent Publication (A) No. 2001-316176) discloses to use a fine dielectric powder having BaTiO3 as its main ingredient and limit the maximum grain size and grain size distribution so as to obtain a fine dielectric ceramic exhibiting good electrical characteristics. By making the dielectric ceramic finer, a higher reliability can be obtained.
However, in Document 2, a thickness of the dielectric ceramic layers of 30 μm is envisioned. When making the dielectric ceramic layers a thin 3 μm or less, a reliability satisfying the demands of the market probably cannot be obtained. For example, in Document 2, Mn or Mg or another sub ingredient is added in a very large amount, but if excessively adding an additive composition, donor or acceptor ingredients segregate at the crystal grain boundaries etc. and therefore the multilayer ceramic capacitor probably drops in reliability. That is, with the method described in this Document 2, when making the dielectric layers thinner, problems such as an increase in insulation defects or a drop in the lifetime or other aspects of reliability are expected.
Further, Document 3 (Japanese Patent Publication (A) No. 11-302071) and Document 4 (Japanese Patent Publication (A) No. 2002-29836) disclose using a main material comprised of a Ba1-xCaxTiO3 base material where Ba is substituted by Ca so as to obtain a dielectric ceramic composition satisfying the X7R characteristic and giving a high reliability. However, with the methods described in these patent documents, there is a large deterioration in the capacity with respect to the DC voltage and the demands of the market are not sufficiently satisfied.